Planetary circulations in the presence of transient and self-induced heating

The research program focuses on large-scale circulations and their interaction with the global convective pattern. An 11-year record of global cloud imagery and contemporaneous fields of motion and temperature have been used to investigate organized convection and coherent variability of the tropical circulation operating on intraseasonal time scales. This study provides a detailed portrait of tropical variability associated with the so-called Madden-Julian Oscillation (MJO). It reveals the nature, geographical distribution, and seasonality of discrete convective signal, which is a measure of feedback between the circulation and the convective pattern. That discrete spectral behavior has been evaluated in light of natural variability of the ITCZ associated with climatological convection. A composite signature of the MJO, based on cross-covariance statistics of cloud cover, motion, and temperature, has been constructed to characterize the lifecycle of the disturbance in terms of these properties. The composite behavior has also been used to investigate the influence the MJO exerts on the zonal-mean circulation and the involvement of the MJO in transfers of momentum between the atmosphere and the solid Earth. The aforementioned observational studies have led to the production of two animations. One reveals the convective signal in band-pass filtered OLR and compares it to climatological convection. The other is a 3-dimensional visualization of the composite lifecycle of the MJO. With a clear picture of the MJO in hand, feedback between the circulation and the convective pattern can be diagnosed meaningfully in numerical simulations. This process is being explored in calculations with the linearized primitive equations on the sphere in the presence of realistic stability and shear. The numerical framework represents climatological convection as a space-time stochastic process and wave-induced convection in terms of the vertically-integrated moisture flux convergence. In these calculations, frictional convergence near the equator emerges as a key to feedback between the circulation and the convective pattern. At low latitudes, nearly geostrophic balance in the boundary layer gives way to frictional balance. This shifts the wave-induced convection into phase with the temperature anomaly and allows the attending heating to feed back positively onto the circulation. The calculations successfully reproduce the salient features of the MJO. They are being used to understand the growth and decay phases of the composite lifecycle and the conditions that favor amplification of the MJO

Stone-Wales Transformation Paths in Fullerene C60

The mechanisms of formation of a metastable defect isomer of fullerene C60 due to the Stone-Wales transformation are theoretically studied. It is demonstrated that the paths of the "dynamic" Stone-Wales transformation at a high sufficient for overcoming potential barriers) temperature can differ from the two "adiabatic" transformation paths discussed in the literature. This behavior is due to the presence of a great near-flat segment of the potential-energy surface in the neighborhood of metastable states. Besides, the sequence of rupture and formation of interatomic bonds is other than that in the case of the adiabatictransformation.Comment: 10 pages, 6 figure

Compiling a Comprehensive EVA Training Dataset for NASA Astronauts

Training for a spacewalk or extravehicular activity (EVA) is considered hazardous duty for NASA astronauts. This activity places astronauts at risk for decompression sickness as well as various musculoskeletal disorders from working in the spacesuit. As a result, the operational and research communities over the years have requested access to EVA training data to supplement their studies

Instantaneous Normal Mode analysis of liquid HF

We present an Instantaneous Normal Modes analysis of liquid HF aimed to clarify the origin of peculiar dynamical properties which are supposed to stem from the arrangement of molecules in linear hydrogen-bonded network. The present study shows that this approach is an unique tool for the understanding of the spectral features revealed in the analysis of both single molecule and collective quantities. For the system under investigation we demonstrate the relevance of hydrogen-bonding ``stretching'' and fast librational motion in the interpretation of these features.Comment: REVTeX, 7 pages, 5 eps figures included. Minor changes in the text and in a figure. Accepted for publication in Phys. Rev. Let

Instantaneous Normal Mode Analysis of Supercooled Water

We use the instantaneous normal mode approach to provide a description of the local curvature of the potential energy surface of a model for water. We focus on the region of the phase diagram in which the dynamics may be described by the mode-coupling theory. We find, surprisingly, that the diffusion constant depends mainly on the fraction of directions in configuration space connecting different local minima, supporting the conjecture that the dynamics are controlled by the geometric properties of configuration space. Furthermore, we find an unexpected relation between the number of basins accessed in equilibrium and the connectivity between them.Comment: 5 pages, 4 figure

Risperidone-induced weight gain is mediated through shifts in the gut microbiome and suppression of energy expenditure

AbstractRisperidone is a second-generation antipsychotic that causes weight gain. We hypothesized that risperidone-induced shifts in the gut microbiome are mechanistically involved in its metabolic consequences. Wild-type female C57BL/6J mice treated with risperidone (80μg/day) exhibited significant excess weight gain, due to reduced energy expenditure, which correlated with an altered gut microbiome. Fecal transplant from risperidone-treated mice caused a 16% reduction in total resting metabolic rate in naïve recipients, attributable to suppression of non-aerobic metabolism. Risperidone inhibited growth of cultured fecal bacteria grown anaerobically more than those grown aerobically. Finally, transplant of the fecal phage fraction from risperidone-treated mice was sufficient to cause excess weight gain in naïve recipients, again through reduced energy expenditure. Collectively, these data highlight a major role for the gut microbiome in weight gain following chronic use of risperidone, and specifically implicates the modulation of non-aerobic resting metabolism in this mechanism

Endogenous Wnt/β-Catenin Signaling Is Required for Cardiac Differentiation in Human Embryonic Stem Cells

Wnt/beta-catenin signaling is an important regulator of differentiation and morphogenesis that can also control stem cell fates. Our group has developed an efficient protocol to generate cardiomyocytes from human embryonic stem (ES) cells via induction with activin A and BMP4.We tested the hypothesis that Wnt/beta-catenin signals control both early mesoderm induction and later cardiac differentiation in this system. Addition of exogenous Wnt3a at the time of induction enhanced cardiac differentiation, while early inhibition of endogenous Wnt/beta-catenin signaling with Dkk1 inhibited cardiac differentiation, as indicated by quantitative RT-PCR analysis for beta-myosin heavy chain (beta-MHC), cardiac troponin T (cTnT), Nkx2.5, and flow cytometry analysis for sarcomeric myosin heavy chain (sMHC). Conversely, late antagonism of endogenously produced Wnts enhanced cardiogenesis, indicating a biphasic role for the pathway in human cardiac differentiation. Using quantitative RT-PCR, we show that canonical Wnt ligand expression is induced by activin A/BMP4 treatment, and the extent of early Wnt ligand expression can predict the subsequent efficiency of cardiogenesis. Measurement of Brachyury expression showed that addition of Wnt3a enhances mesoderm induction, whereas blockade of endogenously produced Wnts markedly inhibits mesoderm formation. Finally, we show that Wnt/beta-catenin signaling is required for Smad1 activation by BMP4.Our data indicate that induction of mesoderm and subsequent cardiac differentiation from human ES cells requires fine-tuned cross talk between activin A/BMP4 and Wnt/beta-catenin pathways. Controlling these pathways permits efficient generation of cardiomyocytes for basic studies or cardiac repair applications

Isolation and Mechanical Measurements of Myofibrils from Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Summary: Tension production and contractile properties are poorly characterized aspects of excitation-contraction coupling of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Previous approaches have been limited due to the small size and structural immaturity of early-stage hiPSC-CMs. We developed a substrate nanopatterning approach to produce hiPSC-CMs in culture with adult-like dimensions, T-tubule-like structures, and aligned myofibrils. We then isolated myofibrils from hiPSC-CMs and measured the tension and kinetics of activation and relaxation using a custom-built apparatus with fast solution switching. The contractile properties and ultrastructure of myofibrils more closely resembled human fetal myofibrils of similar gestational age than adult preparations. We also demonstrated the ability to study the development of contractile dysfunction of myofibrils from a patient-derived hiPSC-CM cell line carrying the familial cardiomyopathy MYH7 mutation (E848G). These methods can bring new insights to understanding cardiomyocyte maturation and developmental mechanical dysfunction of hiPSC-CMs with cardiomyopathic mutations. : In this article, Pioner and colleagues reported contractile properties of isolated myofibrils from hiPSC-CMs with highly mature morphology. This approach permits quantitative assessment of maturation and contractile properties of hiPSC-CMs and can be used to study the development of contractile dysfunction in genetically based cardiac diseases. The authors present a patient-derived cell line carrying a novel familial cardiomyopathy MYH7 mutation (E848G)

Sequential activation of different pathway networks in ischemia-affected and non-affected myocardium, inducing intrinsic remote conditioning to prevent left ventricular remodeling

We have analyzed the pathway networks of ischemia-affected and remote myocardial areas after repetitive ischemia/reperfusion (r-I/R) injury without ensuing myocardial infarction (MI) to elaborate a spatial- and chronologic model of cardioprotective gene networks to prevent left ventricular (LV) adverse remodeling. Domestic pigs underwent three cycles of 10/10 min r-I/R by percutaneous intracoronary balloon inflation/deflation in the mid left anterior descending artery, without consecutive MI. Sham interventions (n = 8) served as controls. Hearts were explanted at 5 h (n = 6) and 24 h (n = 6), and transcriptomic profiling of the distal (ischemia-affected) and proximal (non-affected) anterior myocardial regions were analyzed by next generation sequencing (NGS) and post-processing with signaling pathway impact and pathway network analyses. In ischemic region, r-I/R induced early activation of Ca-, adipocytokine and insulin signaling pathways with key regulator STAT3, which was also upregulated in the remote areas together with clusterin (CLU) and TNF-alpha. During the late phase of cardioprotection, antigen immunomodulatory pathways were activated with upregulation of STAT1 and CASP3 and downregulation of neprilysin in both zones, suggesting r-I/R induced intrinsic remote conditioning. The temporo-spatially differently activated pathways revealed a global myocardial response, and neprilysin and the STAT family as key regulators of intrinsic remote conditioning for prevention of adverse remodeling